Beefed-up enforcement of U.S. gun controls in the Washington area has coincided with a reduction in gun-related crimes, the Treasury Department's Bureau of Alcohol, Tobacco and Firearms reported yesterday.

The bureau released a flury of statistics to suggest that its Operation CUE (for "Concentrated Urban Enforcement") program in the Washington, Boston and Chicago metropolitan areas his begun biting into firearms markets for criminals.

The federal agency quoted a private consultant's report as concluding that Operation CUE "has contributed significantly to a reduction in major violent crime committed with firearms" in the Washington area during its first 10 1/2 months through last December.

However, details of the consultant's report by BDM Corp. of Vienna, showed only limited evidence so far that Operation CUE has helped reduce gun-related crimes. While the federal enforcement effort covers the entire metropolitan area, for example, bureau officials acknowledged that BDM used crime data for the city of Washington alone.

The Treasury agency's own report cited FBI data showing that violent crimes in the Washington area - including Maryland and Virginia suburbs - declined 16.5 per cent in the January-June period of last year, when Operation CUE was getting under way from the corresponding 1975 period. It was unclear whether those crimes all involved use of guns.

The bureau's report cited Washington city crime data from District of Columbia police for the July-September, 1976, quarter showing murder by firearms down 32 per cent, robbery by firearms down 30 per cent, and assault by firearms down 10 per cent from the same year-earlier period.

The report called it "particularly significant" that rates for these same crimes involving weapons other than firearms failed to decrease as steeply.

The Treasury Department bureau reported other data to indicate that Operation CUE has affected the Washington area crime-gun market.

Handguns have declined to 68 per cent of all crime-related firearms confiscated by area police, down from 77 per cent before Operation CUE began. The percentage of rifles and shotguns, including sawed-off weapons, has increased correspondingly.

Thefts of handguns, rifles and especially shotguns have increased at higher rates than before. Use of stolen handguns in armed robberies has more than doubled in percentage terms.

The percentage of "new" firearms (two years old or less) used in crimes has decreased, with the percentage of older weapons increasing. Some authorities view this as evidence of effective enforcement pressure against normal sources of guns used in crime.

Bureau officials said Operation CUE has involved deploying an increased number of agents to investigate and crack down on illegal firearms sources, prepare cases for prosecution, trace all crime-related guns and step up compliance checks on federally licensed dealers.

"We can state positively that crime guns and explosives, and the criminals who use them, are being taken off the streets at an accelerated rate since CUE began," said Rex D. Davis, the bureau's director.